AUTHOR=Li Haoyu , Li Baoshuai , Zhuang Xingang , Chen Lingyun , Wu Bin , Zhao Luo , Zhu Xingbang , Gao Yesheng , Wu Hengkui TITLE=High-efficiency spot size converter for photonic crystal fiber-to-waveguide using composite waveguide structures JOURNAL=Frontiers in Physics VOLUME=12 YEAR=2024 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2024.1515157 DOI=10.3389/fphy.2024.1515157 ISSN=2296-424X